Process of extracting potash from saline deposits and brines



ducing potash in a manner sufficiently eco nomical to be practicable' funder ordinary the brine.

EARL P. STEVENSON, OF CAMBRIDGE.

MASSACHUSETTS, ASSIGNOR, BY MESNE ASSIGNMENTS, TO GENERAL BOND AND SHARE COMPANY, OF BOSTON, MASSA- CHUSETTS, A CORPORATION OF DELAWARE.

PROCESS OF EXTRACTINGPOTASH FROM SALINE DEPOSITS AND BRINES.

misses.

No Drawing. Application filed August 7,

To all whom it may concern.

Be it known that I, EARL P. STEVENSON,

a citizen of the United States, residing at Cambridge, in the county of Middlesex and State of Massachusetts, have invented. cer tain Improvements in a Process of Extracting Potash from Saline Depositsand Brines, of which the following description is a sp ification. 3

-This invention relates to the recovery of potash from the saline depositsa'nd brines' of certain lakes in the western part of this country and it is particularly concerned with the recovery of potash from Searles Lake, California. This lake .consists es sentially of a deep salt deposit'covering a very large area and permeated with brine up to a point Within a few inches of the surface. Various attempts have been madeheretofore to recover potash from'thisjbrine or from the salt deposits ;of thisleleee-but none of these attempts, so far as I havebe'en; able to learn,-have been successful in promarket conditions. a 4 It is the chief object of the presentinven-; tion to devise a practical. process suitable for practice on a commercial scalefor e'conomically extracting potash from this and similar brines. It is also an object of the invention to devise an 'eflicient and economical method of eliminating carbonates from such brinesiregardless ofthe constituent which it is desired to extract from The brine treated may consist eitherof the natural brine or it may be. a brine made by dissolving the saline de posits of one of these salt beds or lakes.

Searles Lake brine is essentiallya solution containing the elements of sodlum chloride, sodium sulphate, sodium carbon} ate, potassium chloride and borax. There are also present/in traces other-chemical elements which, however, need not be ,con-

sidered here. Of these chief ingredients the potassium chloride or muriate' of potash 'is the most important commercially and is the material with whichthe present invention-is concerned. Accordingly, the other salts," some of which, however, possess commercial value, may, so far as the present applica-' tion is concerned, be regarded as waste salts. -The problem present, therefore, is. to

Specification of Letters Patent.

' separate the potassium Patented m a, 1922.

1919. S eria1No. 315,8' 76.

W e' from the remalning salts and from the water in which all of these salts are held in solution by a process suflicientlyecoriomical to make it practicable. Furthermore, sincejone of the most; important commercial uses of -potas-- sium chloride is asa fertilizer, it is very desirable that this materialbe'extracted or. recovered in a relatively pure condition; and it is particularlydesirable that it'shall not contain any. great percentage of either borax or sodiumcarbonate. That is, borax in excess of 1-% is, by some authorities, consid er'ed injurious to plant life, while anYfsubstantial percentage of sodium carbonate'may be objectionable in some fertilizers.

Considering the possible mixtures of;salts present. in the brine, the simplest mixture from which the potassium chloride can be extracted is a mixture wth sodium chloride. Accordlng to the present process, therefore,

it; is. proposed first to treat thelbrine to' substantially eliminate the waste salts other than sodium chloride and thus to leave in the brine ,essentiall'ya mixture of potassium chloride and sodium chloride only. This mixture of salts is then treated to separate the potassiumchloride. 7

For the purpose of disclosing theprocess somewhat more clearly than would otherwise be possible, it will be herein described in connection with the treatment of a specific sample of Searles Lake brine, although it will readily be appreciated that the composition of the brine may vary. in different parts of the lake and under different conditions. The sa'mple'to be considered analyzes substantiallyas follows: 4

p I Percent. Sodiumchloride, N aCl 17.75

, Sodium sulphate, Na,-SO 4.46

Sodium carbonate, Na,CO 4. 97 Borax, Na B,O 1.42 Potassium, chloride, KCL 4. 65

For the purpose of eliminating the waste 10o salts the brine is first chilled sufliciently to precipitate the greater part of the sulphate, carbonate, and borate. The percentages of.

these substances that will be'eliminated' in this manner will vary with the degree to which the'temperature of the-brine is reduced, but this point 'will be determined not only by the elimination of waste salts but also, to some extent, by considerations of economy and the conditions under which the process is practised. llnder moston- "ClllllSttLIlCQS the most satisfactory temperature apiiears to be between -15 C. and 20 I find that after the sample of brine above referred to has been chilled to -15 C. and the precipitate filtered off, the remaining brine has a composition substantially as follows:

x Per cent.

Na,SO, .61 M3 0 -.s1- Ni co 1,.5'5 NaCl 18.15 KCL 6.57

The potassium chloride does not separate as a solid at this temperature, nor even at a chilling operation, the brine is next treated with a suitable precipitant for these sub stances, preferably calcium sulphate; Considerations of availability and expense make it usually advisable to use calcium sulphate in the form of gypsum. Towersv may be packed with gypsum and, the brine run through them. This treatment eliminates all the sodium carbonate 'lhe brine is filtered to remove anyf'sqlid 'matter and the filtrate is next evaporated to dryness, pref- 'erablyby solar evaporation, thus producinga low grade potassium 'salt for wh ch there. is aflimited market. By evaporating the brine to drynessfwhich can readily beaccomplished by natural or solar evaporation,

the" diflicult and expensive operations in- 'volved in'the separation of the salts by a high temperature evaporation are eliminated from my process with gypsum before the chilling operation has been performed instead of afterwards,

as just described, and thetreatment before chilling has the advantage that a more ef; ficient separation. of the borax takes place during the chilling operation. On the other hand, the quantity of gypsum required to treat the brine before it is chilled is so much greater than that required after chilling that I consider it preferabl'aunder most circumstances, to use the gypsum treatment after the chilling operation has been completed.

For most purposes a higher grade of potash than that produced simply by following sodium carbonate.

the steps above described is required. it will be seen that this dry mixture of salts consists chiefly ofpotassium chloride and sodium chloride with very small percentages of sodium sulphate and borax. In order to separate the potassium chloride from the other salts I prefer to extract this mixture of salts with a liquor saturated with sodium chloride and calcium sulphate. This may be done in a suitable apparatus by running the extraction liquor, preferably heated to 'a temperature of about 100 C., through the mixture of salts until all of the potassium chloride has been dissolved out and the liquor is substantially saturated with potas sium chloride. This hot saturated liquor is 1 drawn off through a filter which removes the undissolved salts and it is then cooled to ordinary temperatures when the potassium chloride separates out due to the fact that the solubility of potassium chloride in such a solution decreases with a 'decrease in temperaturewhile the solubility of sodium chloride increases with a decrease in temperature.

-This' potassium chloride erop is filtered off i and the'extraction liquor is used over and over again to extract successive crops of po tassium chloride. It is obvious that as the extraction liquor is used in successive cycles. it may become contaminated with substances other than those desiredinthe extraction.

process. These 'substances, however, do not ordinarily interfere with this process.

- While the potassium chloride in separating from a concentrated solution of sodium chloride and sodium sulphate will occlude and adsorb some of the latter substances from the solution, still it is possible by this process to obtain a grade of muriate of I potash which compares very favorably with v able grinder)" This mixture is then extracted It is obvious that the brine may be treated for its-potassium chloride content with a solution saturated with sodium chloride and i calcium sulphate. The undissolved salts are filtered out of the hot extraction liquor and the liquor-is then cooled to crystallize out. the potassium chloride, as above described. The'cal'cium sulphate performs the same function here as in the process above described, namely, that of precipitating the lVhile some potassium. sulphate is formed due to the gypsum treatment, this salt is in no wise objectionable. A very small percentage of this potassium sulphate will crystallize out of the extraction liquor with the potassium chloride. In

. extract-ion liquor. The potassium chloride is very soluble and consequently is quickly theprocess of extracting the potassium chlotaken up by the extraction liquor and the fact that the borax is takencup only very slowly in an extraction liquor of the character here used, results in producing a much purer grade of potassium chloride than otherwise would be possible.

While this process has been herein described as applied to the recovery of potash from Searles Lake brine, it will be' readily appreciated by those skilled'in this art that lakes.

the process is applicable to a great variety of brines, such as those found in many lakes in the western part of the country and those made by dissolving salts from salt beds and Consequently, will be understood that the term Searles' Lake brine as used in the appended claims identifiesthe type of brine to which the present invention is applicable rather than brine necessarily taken froin Searles Lake. It will also be understood that some features of this process, especially that of removing the sodium carbonate from the brine, are applicable to processes for recovering constituents of value otherthan potash from the brines of the character hereinreferred to.

What is claimed as new is:

l. The process of extracting potash from Searles Lake brine which consists in chilling the brine to eliminate a substantial percentage of the waste salts contained therein, evaporating the remaining brine to dryness,

' -mixing the dried salts so retained with a precipitant for waste constituents of the dried salts, and then extracting said mixture for its potash content.

. 2. The process ofextracting potash'from.

Searles Lake brine which consists in chillingthe brine to eliminate a substantial percentage of the waste salts contained therein,

evaporating the remaining. brine to dryness and then treating the dried mixture of salts so obtained to remove the potassium chloride from the, mixture and using calcium sulphate in said treatment-to'preeipitate the sodium oarbonate'content f said mixture.

3. The'proces'sof extracting "potash from Sea-rles' Lake brine which consists in chilling the brine to "eliminate a substantial percentage of the waste salts contained therein,

evaporating the remaining brine to dryness,

mixing gypsum with the dried salts so ob tained, treating the mixture thus produced cooling the hot solution to cause the potas-' si'ur'n chloride to crystallize out.

4. The process of extracting potash from Searles Lake brine which Iconsistsin chilling the brine to remove aa substantial percentage of the waste salts, treating the remaining brine with calcium sulphate to effect a'further elimination of the waste salts from the brine, and evaporating the remaining brine to dryness. I

5. The process 'ofextracting potash. from Searles Lake brine which consists in chilling the brine to remove a substantial percentage of the waste salts, filtering off the precipitate, treating the filtrate with calcium sulphate to effect a further elimination of the waste salts. thus leaving the brine richin potassium chloride and sodium chloride, evaporating the brine to dryness, and then treating the dried salts to separate the potassium chloride; v 1

6. The process of extracting potash from Searles Lake brine which con'sists in chilling the brine to remove a substantial percentageof the wastesalts, treating the remaining brine with calcium sulphate to effeet a further elimination of the waste salts from the brine, evaporating the remaining brine to dryness, by'solar evaporationand extracting the resulting mixture of salts-for its potashcontent. v

.7. The processof extracting potash from Searles Lakebrinewhich consists in chilling the brine to remove a'substantial percentage'of the waste salts, treating the re- -maining brlne with calcium sulphate to, et-' feet a further elimination of the Waste "salts.

fromfthe brine, evaporating the remaining brine to dryness, and extracting the resulting mixture of salts for its potash content with'a saturated. solution of calcium sulphate and sodium chloride.

'8. The process of extracting potash from Searles Lake brine which-consists in chilland cooling. the filtrate -to precipitate the.

potassium chloride.

9. The process ofextracting potash from Searles Lake brine which consists in chilling the brine to eliminate a substantial percentage of the waste salts contained therein, evaporating the remaining brine to dryness by solar evaporation, mixing calcium sulphate with the dried salts so obtained,

.treating the mixture thus produced with a hot extraction liquor from which the po tassium salts will crystallize o-ut'substantially unaccompanied by other salts, and

10. The process of extracting potash from Searles Lake brine which comprises the following steps, nari1ely,.chilling the brine to eliminate a substantial percentage of the Waste salts contained therein, evaporating the remaining brine to dryness,'extracting the resulting mixture of dried salts for its 10 potash content, and at some stage of the process adding calcium sulphate to the material undertreatment to substantially eliminate the carbonate constituents of the brine.

In testimony -whereof I have signed my 15 name to this specification.

EARL PI. STEVENSON. 

